Stella's magic took hold of the cube and the thing inside it, which Twilight still hadn't gotten a good look at, and levitated them towards herself. "Tomorrow," she said, in her waving, shifting tone. "Tomorrow, in front of the castle." She was still and silent for a couple of seconds. Images appeared in front of her, for everyone else to see as well, the five cities she had trapped and the bubbles around them disappearing.
Stella opened her mouth again as the images faded away. Those present heard her voice twice as she spoke, one of the instances louder and distant and more distorted, and quickly they realised it was because it was being projected to the outside as well. Those closest to the windows could spot hints of some projection of sorts she was also putting there. "Tomorrow, at midday, in front of the castle in Ponyville."
Twilight sucked in a breath as she realised what Stella was doing. Judging by the way she was speaking, she was broadcasting herself all over the country, not just outside the building. She'd just shown she was able to reach that far with her magic after all.
"I will fight your illegitimate ruler Twilight Sparkle for control of Equestria," Stella continued. "The winner will be decided as one of the participants either surrenders, or is rendered physically unable to continue the fight. Failure to be present will be considered as a loss. A refusal to fight willl be considered a loss. Running away will be considered surrendering. Should Twilight Sparkle win, she will maintain her title and powers. Should she lose, I will replace her."
She teleported the cube away, and slowly made her way across the room towards Twilight. Once she was standing in front of her, looking directly into her eyes, her horn shone differently and Twilight felt some of the magic being pointed towards her face. "Do you accept the terms of our agreement?" Stella asked. "If you wish to surrender now, you are free to do so." Stella was smirking.
Twilight knew she wasn't expecting her to surrender. Twilight knew she couldn't surrender. And as much as she also knew doing so and playing outside of Stella's schemes would have driven the alicorn insane, the consequences for it would have been too much to be worth it. The other wanted a fight and she'd force it out of her, and if Twilight didn't collaborate ponies would be hurt. As much as showing Equestria the kind of monster they were dealing with might help her, the risk was too great. "I accept," Twilight said.
Stella disappeared, everyone fell to the floor. Twilight was glad there were already orders in place to not let anyone but Sunset and a few others in. She turned to the nearest guard. "Have the previously designated cities evacuated regardless, and proceed with evacuating Ponyville as well."
He nodded to her and walked away in a hurry. Twilight looked to the ground, then teleported away.